(a) Field of the Invention
This invention relates to a rare earth-iron-boron-based permanent magnet having a large maximum energy product BH.sub.max.
(b) Description of the Prior Art
A rare earth-cobalt-base magnet composed of, for example, R.sub.2 (CoCuFeM).sub.17 in well-known as a high performance magnet. This rare earth-cobalt-based magnet has the maximum energy product (BH.sub.max) of 30 MGOe at most. Recently, there has been a strong demand for more compact electron implements with high performance. There has also been a great need for a high performance magnet with a far higher maximum energy product BH.sub.max. However, such rare earth-cobalt-based-magnets require heavy consumption of relatively expensive cobalt.
To meet the above-mentioned requirements, research has been ongoing in various entities in this particular field to develop a rare earth magnet mainly consisting of iron (refer to, for example, patent disclosure Sho 59-46008). This permanent magnet substantially consists of iron, and contains boron and rare earth elements such as neodymium and praseodymium. The developed magnet can provide a sample whose BH.sub.max has a larger value than 30 MGOe. This product mainly composed of less expensive Fe than Co ensures the manufacture of a high performance magnet at low cost, and is consequently regarded as very hopeful magnetic material. For further elevation of magnetic performance, various studies have been undertaken, for example, addition of Co (patent disclosure Sho 59-64733), addition of Al, Ti, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo, Ge, Sb, Sn, Bi, Ni (patent disclosures 59-89401 and 59-132104) and addition of Cu, S, C, P (patent disclosures 59-132105 and 59-163803), and the combinations of the above listed materials (patent disclosures 59-163804 and 59-163805).
However, the above-mentioned rare earth-iron-based permanent magnets are more strongly demanded to display a for larger maximum energy product BH.sub.max, and research and development are being carried on in various quarters of this particular industry.